- Red is the color of warmth, for instance used to indicate warmer areas on a weather
map, or for heat-related warnings.
- Red catches people's attention, and is often used to indicate danger or emergency.
- Red is the color of heat and fire. Taps for hot water are often labeled red. Red is commonly the color of fire alarm boxes, fire extinguishers, and the firefighter profession itself.
- Red denotes "stop" in, for instance, stop signs, traffic signals, brake lights, or the flashing lights of a school bus.
- A Red Cross or Red Crescent signify medical personnel, facilities, or equipment, or the Geneva conventions.
- Red indicates extreme danger on Western color-coded scales, such as wildfire hazard signs or the U.S. Homeland Security Advisory System.
- In auto racing, a red flag signals all cars to immediately stop. The redline is the maximum speed an engine and its components can run.
- Emergency exits on passenger aircraft are indicated by red signs and lighting.
- "Redlining" is delineating a forbidden area (as on a map), for instance where a company denies or increases the cost of services, and is illegal in various circumstances in the U.S.
- In religion, Red also represents the color of fire and so symbolizes the presence of God. It is the liturgical color for Pentecost. It is also considered the color of the Church, since red can also symbolize the blood of martyrs. It is sometimes used for Holy Thursday and during Eastertide. In Catholic tradition it is used for Palm Sunday in anticipation of the death of Jesus.
- In Association football (soccer), the referee shows a red card to a player who is being sent-off. Red is the color of both romantic and carnal love, thus the red of a valentine heart and of a "red-light district". But it may also denote anger, as in the expression seeing red, or embarrassment, as in being red-faced.
- Being the color of blood, red was associated with the Roman mythology god of war, Mars, and the reddish planet Mars became named after him. The phrase "red-blooded" describes someone who is audacious, robust, or virile; it is sometimes used to contrast with a cold or effete "blue blood" although the terms are unrelated in origin.
- In English heraldry, red denoted ardent affection or love, while crimson (blood-color) stood for boldness, enthusiasm, or impetuosity. (The American Girls Handy Book, p. 369-370)
- Before the French revolution red was the color of the flag signifying the imposition of martial law.
